Method of making nitric acid.



UNITED STATES Warxrm: IV 1 [.LR. (W i or CAR'JERSVI Patented-March 22, 1904.

LONDON, isxtimxn, .issmxoa o A. o. GRANCHiR,

LLB, GEURLHA- METHOD OF MAKING NITRloAcio.

I SPECIFICATION forming part f Letters Patent No. 755,378 dated March 22 1904 Applicant-u filed May 25, 1909 Renewed Yehr'srry 2'1,

To'all wlmnz it may concern:

Be it known that I, WALTER Mitts, asuhjcct of the King of Great Britain, rcsidingiin Lon don, England, have invented certain new and iuseful Improvements in the Manufacture of Nitric Acid,oi' which the following is a specification.

This invention relates to a method or process 'of preparing nitric acid from salts or compounds naturally occurring or otherwise and containi-"g the acid by [irstcol'n'c'rting the nitrate into nitrate of lead.and is based upon the discovery that lead not only in its metallic condition, but as it exists in its ores- (cspecially galena and c'crusite) is'attacke'd and dissohed by hydrofiuosilicic acid when that acid issulii'cien tlyconcentrated, and particularly when the concentrated acid is heated.

In carryingout thc present process of ma n ufacturing nitric acid I place excess of scrap lead or crushed ore in a pan or other receptacle, and having added thereto aproper amount of acid heat isiapplied until the niass is substantially dry." I fi'nd in practice that the warm acid begins to attack and dissolve the substance when the specific gravity of the acid is about 1.80, and in the event that scrap lead is employed the action of the acid is somewhat accelerated hyhlowing air thr ugh the mixture. If warm water 1 is now added to the dried mass, an aqueous solution of silicofluo rid of lead is obtained, which after being filtered is ready for use; The next step in the practiceof the present process consists in the preparation of'an aqueous solution of nitrate of lead from the solution of silicofluorid. This is usually accomplished in prac tice by adding thereto the nitrates of the elements calcium, potassium, or sodium cit-her in aqueous solution or in a line state of division. The silicofiuorid of the respective metal is precipitated, while nitric of lead remains in' solution. ,Fronrthis solution of nitrate of lead nitric acid-may be formed by. adding sul- {uric acid, the reaction taking place as indiicate'd by the equation 1904. Serial No. T91110- (No spcciniens.)

The strength of the nitric acid thus produced depends upon the specific gravity of the=liquids a result of the reaction is precipitated. The solution of nitric acid may be drained therefrom and afterward concentrated by evaporation. which is found to he asatisfactory means Sulfate of lead being slightly soluble in concentrated nitric acid. the solutions employed should not he too strong. it is advantageous cilic gravity of about 1.80; in then reacting upona solutionof IhG'SlliCOllllOl'lCl of lead so formed to form nitrate of lead; and in then separating the nitric acid from the nitrateof; lead.

The process of manufacturing nitric acid fluosilici'c'acid; in then reacting upon a soluform nitrate of. lead: and in then separating the nitrieacid from the nitrate of lead.

Signed at Nos. to 15 llurn-iystrect, New York, l\' Y., this 23d day of May, 1903.

"npxL'rnn nlLts.

\Vitnesses:' Faun. J. Dom-1,

Jonx 0. 5121mm.

employed. The sulfate of'lcad p oduced as 59 of obtaining the concentrated acid, especially 5 5 when the evaporation is cenductcdi n. cacao also to keep the sulfuric acid in' excess-when 6O silicofiuorid of lead with a' salt 79' stances in hydrofiuosilicic acid having a spewhich consists in heating a mixture of a leadcarrying suhstanceand concentrated hydrotion of the 'sil'icofiu'lrid of lead soforined to 5 

